The invention relates to communications systems generally and, more particularly, the invention relates to an apparatus and method for distributing digital information, such as MPEG-like data, over an analog system having an analog infrastructure.
Existing television studios or TV plants, by and large, use analog video signals carried over 75-ohm coax to convey signals around their plant. Each television studio has a large investment in its infrastructure such as routing xe2x80x9cgridsxe2x80x9d which allow signal routing to be changed as needed within the plant.
With the proliferation of digital television signals, these costly existing analog infrastructures are incompatible in dealing with digital information. A small fraction of TV plants have converted over to the newer xe2x80x9cSDIxe2x80x9d 270 Mb/s digital system (SMPTE 259M) for conveying uncompressed digital standard definition video, and additional standards are emerging (e.g., SMPTE 305M) that define how to use this infrastructure to convey all kinds of other data, especially compressed video. The reluctance or slow pace of conversion to an all-digital infrastructure is due substantially to cost and the large investment in the analog infrastructures. As such, the majority of current TV stations still operate all-analog infrastructures. Thus, it would be very advantageous if digital information such as Advanced Television Systems Committee (ATSC) signals can be routed within the existing analog infrastructures.
Therefore, there is a need in the art for an apparatus and method for distributing digital information over an analog system having an analog infrastructure.
An embodiment of the present invention employs an interface, e.g., a modem-like interface for converting a digital information signal into an analog signal for use within an analog television studio infrastructure. Specifically, digital data is converted into a National Television Systems Committee (NTSC)-like waveform that uses the active video portion of the signal to carry the digital data. Namely, the present invention employs a novel modulator that conveys compressed video data into analog video lines by creating an analog xe2x80x9cvideoxe2x80x9d signal that contains video gray-scale levels which correspond to digital data values, instead of containing an image. The data is represented in a manner that is robust and is capable of withstanding the distortions that it may encounter on its way through various media, including frequency rolloff, phase distortion, proc amp blanking, clipping, and other video waveform distortion effects.